There are a variety of different types of systems currently available for distributing water for the irrigation of cultivated plants. Likewise, plastic mulch of various types and materials are currently being produced for the landscaping, turf, horticulture, and food production markets.
Drip Irrigation
Of the various forms of irrigation systems, drip or microdrip irrigation is considered to be the most desirable because they have been shown to save water, reduce the use of horticultural chemicals, are relatively insensitive to environmental effects, reduce labor, and promote superior plant growth as compared to other technologies.
Most importantly, drip irrigation is an effective irrigation system in terms of water conservation. With drip systems, water is not wasted by watering areas between rows or from run-off. Furthermore, the problems of excessive evaporation, wind-effects, and overspray are avoided by putting the water directly onto the ground rather than simulating rainfall.
It is noted that other systems, such as wick irrigation and hydroponics, are currently being used but are generally considered cost prohibitive in all applications outside of commercial greenhouses and are not considered pertinent here.
All drip irrigation systems share several things in common. They all generally consist of a central water supply transport means, usually a hose or pipe, and numerous water emission device(s). These emission devices are typically called emitters and are designed to dissipate the irrigation water as evenly as possible at low flow rates, i.e. drips. In addition, drip systems all require relatively fine mesh filtration to avoid clogging of the emitters. Finally, some level of pressure regulation is required as most drip irrigation systems operate at pressures between 8 psi and 15 psi. Drip irrigation systems can be categorized as either line source or point source dissipation systems.
Line source dissipation systems emit the water uniformly along the full length of the main supply hose. A series of small holes or similar means are positioned along the length and serve to dissipate the pressure and thus the water flow down to a drip. Line source systems are often referred to as soaker hose or drip tape.
In the past, various U.S. patents have issued in the field of line source systems. U.S. Pat. No. 3,205,619, issued on Sep. 14, 1965 to J. W. Henry, discloses an irrigation mulching sheet consisting of an integral irrigating means permitting more economical use of available water while improving ease of installation and stability of the structure. Water is continuously provided along the linear tubing of the sheet.
U.S. Pat. No. 3,774,850, issued on Nov. 27, 1973 to David G. Zeman, discloses a polymeric, preferably biodegradable tube for agricultural use for distributing water to plants located along the length of the tube. The tube includes a plurality of outlet openings so as to restrict the flow of water to each of the outlets. The tube may also have mulch sections along the length of the tube. Preferably the walls of the tube are thin enough to be broken up by normal agricultural instruments such as plows. The tube has limited durability.
U.S. Pat. No. 4,095,618, issued on Jun. 20, 1978 to Lloyd Spencer, describes an irrigation rodent deterrent tube, particularly adapted for drip or trickle irrigation. The tube has a flat configuration when free of internal pressure. The tube also has laterally projecting webs which tend to be the first to be bitten by a rodent while exploring the presence of the irrigation tube. The webs may be enlarged to contain a concentration of a deterrent or toxic material.
U.S. Pat. No. 4,199,106, issued on Apr. 22, 1980 to Takatsuiki Susumu Kojimoto et al., discloses an irrigation hose which is produced by melt-sticking double thermoplastic resin film in a plane along longitudinal parallel lines so as to form a supply passage with communicating holes and constant pressure passages with water-irrigating holes. The invention includes aligning the communicating holes and/or water-irrigating holes to provide irrigating water along the hose.
U.S. Pat. No. 4,473,191, issued in September 1984 to Chapin, discloses a drip tape fabricated from thin plastic material. The drip tape incorporates a series of tortuous paths to accomplish the desired pressure drop and flow reduction. The pre-installed or pre-molded dissemination devices, such as emitters, are positioned along the length of the tape.
U.S. Pat. No. 5,839,659, issued on Nov. 24, 1998 to Eric S. A. Murray, discloses a capillary system that provides water, nutrient solutions and gases such as air to the root zone of plants. The system uses one or more conduits having perforations spaced apart therealong, with the conduits being held in pockets. In use, the capillary system is buried to an appropriate depth in soil below the plants to be irrigated. The upper layer of capillary cloth is wet by the flow out of the perforations and serves to distribute water.
Soaker hose devices are another line source irrigation system, often made of particulate matter, such as ground-up vehicle tires, that have been compressed with binder into a semi-solid hose-type material. Alternatively, the soaker hose consists of a flat hose which has been punched with holes after manufacture. Both of these types of soaker hose are relatively expensive and some have been known to disintegrate over a short period of time, thus reception by professional and agricultural consumers has not been good.
Drip tape devices, as disclosed in the prior art, are fabricated from thin plastic material and incorporates a series of tortuous paths to accomplish the desired pressure drop and flow reduction. The pre-installed or pre-molded dissemination devices (emitters or emitter discharge points) are spaced along the length of the device at fixed distances ranging from six inches to 48 inches.
Prior art drip tape is generally inexpensive to manufacture due to the relatively small amount of plastic material being used. Due to the use of low cost materials and thin wall thickness, drip tape is typically designed to last only one or two growing seasons prior to being removed and replaced.
Drip tape lines are often buried a few inches below the surface of the ground to be planted in order to minimize the evaporation of the water from the surface. However, if installed below the surface, these products depend on the capillary action of the soil to override the force of gravity. Therefore, the entire planting bed typically needs to be wetted to fully irrigate the root zones of the plants. As discussed later, plastic agricultural mulch is normally installed over the top of the drip tape to further minimize evaporation and to control weeds.
When drip tape systems have been used for the irrigation of uniformly and closely spaced plants (commercial applications) they have had good reception. They have been quite effective as an irrigation technique and as a water conservation vehicle when compared to overhead spray and furrow systems. Because drip tape distributes water evenly over the entire length of a planting bed, some water is wasted or used by weeds between the plants. Thus there is a need to distribute water precisely to the plants being watered and not the space between while being easy to install.
In applications where plants, in any given plot, can vary in size, spacing, and species, a system having fixed spacing between disseminators such as drip tape may not be preferred due to wasted water. Point Source systems are designed for these “random planting” applications.
The most popular point source drip irrigation systems employ emitters installed in the water transport lines as needed, such that the water is disseminated at specific points where the emitters are placed. An advantage of a point source dissemination system is that the irrigation can be “customized” for any plant spacing or size. That is, plants of different sizes and water requirements can be accommodated in the same watering zone by varying the number of emitters and/or their flow rates.
When plants are spaced 2.5 feet apart or greater, experience has shown that point source drip irrigation is the most effective system for saving water. In fact, the further the plants are spaced apart, the more cost-effective point source drip irrigation becomes, on a relative basis, when compared with overhead spray or furrow irrigation systems. When used in landscaping applications, the main tube and emitter lines can be covered with mulch or bark chips and look quite attractive. Of course, after the plant material has matured, these installations look even more attractive.
Another advantage of a point source drip irrigation system is that it can be installed after the plants are in place. Installation is usually quite easy but extremely time consuming. Thus the major disadvantage of these systems is the labor and material expenses associated with the custom installation. The emitters are also prone to clogging with contaminants in the water due to their small passages so expensive filters and/or constant maintenance is required.
Attempts are being made to modify drip irrigation systems to deliver less water per emitter so that the irrigated plants receive the optimum amount of water over a longer period of the day. These “Ultra Low Drip Irrigation” systems are very complex to operate and clogging represents the major obstacle to achieving the objective of optimum plant growing conditions.
Prior art point source irrigations systems include U.S. Pat. No. 4,126,998, issued on Nov. 28, 1978 to Gideon Gilead, which teaches an irrigation apparatus comprising first and second layers of sheet material. The layers are bonded together at surfaces to define a liquid conduit, having at least one pressure reducing path associated therewith and an exit port from each of the at least one pressure reducing paths. The apparatus is linear and is installed underground.
Thus there is a need for an inexpensive drip irrigation system which does not waste irrigation water between plant sites. There is also a need for a drip irrigation system which is easy to install and remove when no longer needed. Furthermore, there is a need for a drip irrigation system that is able to deliver very small amounts of water at specific plant sites without being prone to clogging.
Mulch
There are various forms of mulch used in the home landscaping industry with additional types produced for commercial agriculture applications. The benefits of mulching include; less water evaporation, less weeds, soil warming and heat retention leading to earlier and higher yields, erosion control, and a more uniform appearance. Types of mulch include organic, plastic film, and irrigating mats.
Organic mulch, such as hardwood bark and pine needles, tend to be the most aesthetically pleasing but quickly degrade in the environment or wash away with heavy rains.
Plastic Film mulch (agricultural film or geotextiles) are effective weed barriers and are preferred in most commercial applications where they can be placed prior to planting. They are very effective at soil erosion abatement and weed control while minimizing surface water evaporation. The perforated or woven versions which are air and water permeable are most desirable but also the most expensive.
Artificial mulch has been disclosed in prior patents, including U.S. Pat. No. 4,833,822, issued on May 30, 1989 to Paul DiGrassi, describing a mulch strip of an elongated base sheet formed from a flexible plastic material having a pair of parallel fluid reservoir tubes extending along the length of each base strip, down the opposite side edges of the strip. Each of the fluid reservoir tubes is provided with a hose fitting for connection with a conventional garden hose for filling the reservoir tubes with water. In use, the water filled tubes serve to hold the mulch strip in place and form a channel for retaining rain water on the surface of the strip. The fluid reservoir tubes also collect heat and serve to keep the ground beneath the strip warm after sunset. A plurality of concentric perforations are spaced along the length of the base sheet for the insertion of plants into the ground through the base sheet.
In commercial farming, thin agricultural film is typically placed over planting beds after drip tape has been installed. This combination has proven to be very effective at producing high yields of quality product with relatively low water use.
Irrigating mats are a recent development in the field of artificial mulch, which employ a layer of water distributing material bonded to the underside of a plastic sheet in order to distribute water over the entire area covered by the mat. The prior art includes U.S. Pat. No. 5,301,633, issued on Apr. 12, 1994 to Thomas G. Lloyd, that teaches a flat and thin bladder device used to cause earthworms to migrate to the earth's surface for easy collection. The bladder is laid flat on the earth's surface and soaks the ground underneath the bladder perforations. Soaking the earth under the bladder causes earthworms to migrate to the surface and they are then easily collected as the bladder is lifted to expose them.
U.S. Pat. No. 6,293,477, issued on Sep. 25, 2001 to Robert J. Chambers, describes an irrigator configured from a flexible or semi-flexible material which can conform to various sizes and shapes of terrain. According to various embodiments of the irrigator, seep holes may be provided. The irrigator contains holes for various plant life to take root through and for facilitating drainage. The irrigator may have multiple, distinct passages for the collection and/or distribution of multiple fluids or gases.
Other related mat devices are taught in U.S. Pat. No. 4,130,245, issued on Dec. 19, 1978 to John D. Bryson and U.S. Pat. No. 5,749,109, issued on May 12, 1998 to Thomas F. Kappel. The Bryson patent teaches a generally flat envelope or package for controllably dispensing into the atmosphere a liquid substance which is normally liquid and vaporizable under atmospheric temperature and pressure conditions. The Kappel patent relates to blankets for use with forced air convection systems, wherein the blankets includes means to provide air through selective areas of the lower sheet of the blanket. These devices relate to using a mat to disburse a fluid throughout the mat, although the application to irrigation and selective plant growth is not addressed.
The failings of prior art irrigation mats include wasting irrigation water between plant sites because the ground becomes soaked without consideration of the location of the plant or root zone of the plant. There is also a need for an irrigation mat which is easy to install and remove when no longer needed. Furthermore, there is a need for an irrigation mat that is able to deliver very small amounts of water at specific plant sites without being prone to clogging. The prior art irrigation mats use materials that are expensive and serve only to redistribute water that is already in the soil rather than actually providing irrigation to the specific plant sites.
Thus, there is a need to combine the water saving benefits of Ultra Low drip Irrigation systems with the many benefits of plastic mulch into an inexpensive, durable, and easy to install product.